The Froude Number, playing with battleships, and the Zulu War – a little known association by Kevin Wall
The grave of Froude. [You must be registered and logged in to see this image.]
There is an association between the Froude Number, a set of highly significant (for naval architecture) manoeuvresthat were conducted in the Mediterranean in 1873
and the Zulu War. It is a fascinating tale that deserves to be told.
Every civil engineer, and every aeronautical engineer and naval architect also, has learned of the Froude Number. Most will assume that it was thus named as a result of the work of one of the pioneers responsible for that late nineteenth century surge (forgive the pun) of knowledge in hydraulics.They would be correct. “The latter half of the century saw a rapid growth in theoretical knowledge in a wide range of hydraulic topics wave motion, pipe and channel flow resistance, gradually varied flow in channels, percolation, ship resistance, sedimentation, pumps and turbines, vortex motion, laminar and turbulent motion, and river model studies. It is not practicable to mention more than a few of those who made lasting contributions, but it is difficult to pass over the German mathematician Helmholtz, Lord Kelvin the physicist, William Froude the model ship experimenter, the engineering professor Osborne Reynolds, the mathematician Sir Horace Lamb and the Americans, James Francis and Clemens Herschel.”Vallentine, 1967, Born in Dartington, Devon, on 28 November 1810, Froude was educated at Westminster School and Oriel College,Oxford. He worked as a railway engineer until 1846 when he began his pioneering work on ship hydrodynamics. “He learned that rolling of ships can be reduced by fitting a deep bilge keel, a finlike projection stretching horizontally along both sides of a ship below the waterline. The device was adopted by the British Navy. After serving in 1868 on a committee to study naval design, he proposed to the British Admiralty a series of experiments using models to determine the physical laws governing full–scale ships.
His proposals were accepted in 1870, and at Froude’s home near Torquay a model–testing tank was built. He discovered that the chief components of resistance to motion are skin friction and wave formation.” (Britannica, 1974,The Froude Number is a dimensionless parameter used to indicate the influence of gravity on fluid motion in
hydrology and fluid mechanics.
To refresh the memory of those of us who took other directions after graduation, the Froude Number enters into formulations of the hydraulic jump (rise in water surface elevation) that occurs under certainconditions and is important in the calculation of critical depth in open channel flow. Froude’s work was (and still is) also invaluable in the testing of ship models and models of harbours and rivers. He developed a method of studying scale models propelled through water and of applying the information obtained to full–size ships. He discovered the laws by which the performance of the model could be extrapolated to the ship when both have the same geometrical shape.
A similar technique was later used by pioneers in aerodynamics, whose tests of models in wind tunnels contributed to the rapid development of aircraft design. Changes in the mid–century Royal Navy The Royal Navy was making a series of drastic changes to the technology that had won it sea superiority. Anxious not to be left behind by the innovations of other navies, the Navy introduced steam (initially only under the hatches of tugs to haul the greater ships in confined waters) in 1821, then the screw–propeller (the famous tussle between the paddle–wheel Alecto and the screw–driven Rattler took place in 1845), and the first iron–hulled ships (also 1845). (As an aside, on this latter innovation the Navy was “ahead of public opinion.
A popular outcry of ‘Hands off our wooden walls’ checked Admiralty enterprise; indeed forced a retreat, and the iron frigates were degraded into troopships. One of them, the Birkenhead, earned notoriety when thus employed, by striking a rock off South Africa in 1852, and 432 soldiers were lost.” Further major innovations in the Royal Navy during this period (again, usually a year or two after a foreign power had taken the plunge) were armour (Warrior, 1860), turrets (i.e., protected casemates which pivoted, allowing the guns to be fired in any direction, rather than the whole ship having to be turned to bring the broadside to bear), and steel hulls (1881). Advanced as she was, Warrior of 1860 “retained two ‘wooden wall’ characteristics. First, despite her engines, she remained a full–rigged sailing–ship. Sail was fighting its last battle, abetted by an Admiralty still reluctant to abandon it.
This was undoubtedly a mistake, but it was not blind obscurantism even then. Steam obviously had many great advantages over Sail, but Sail still retained one indeed still does. No vessel yet built has been as truly sea–enduring as the sailing–ship. She needs neither collier nor tanker – no tender of any kind. Drake, Anson, and Cook has sailed alone for years on end, and all over the world Yet the Admiralty’s solution should have been to provide colliers and coaling–stations, not be retain fullrig.” The Captain The superiority of heavy guns in turrets had been effectively demonstrated in 1862, at Hampton Roads, Virginia, in a duel between the Federal turret ship Monitor and the Confederate broadside ironclad Merrimac. The Monitor carried only two guns, but they were powerful 150– pounder weapons mounted in a steam–operated turret amidships. “The news of the Hampton Roads action led to a demand in England for turrets, and a new wooden three–decker, the Royal Sovereign, was cut down, armoured and fitted with turrets In the meantime Captain Cowper Coles had designed the fully rigged turret ship Captain, launched in 1869. And we had to pay for the error in 1870, when the strange–looking Captain, still full–rigged turned turtle ina not–too–heavy gale (off Cape Finisterre, NW Spain),drowning practically all her crew.” This tragedy underlined “the incompatibility of turrets and sails”.
As a consequence of the general anxiety that arose on safety, it was decided by a special Admiralty committee that exhaustive sea trials should be made on all warship types, and particularly on its largest types, the turret ships (or, as they came to be known, battleships). Selected for the most intensive trials was the battleship Devastation (designed by Sir E J Reed), launched in 1871, but sailless and almost mastless – the first Royal Navy battleship to bedesigned without auxiliary sail power.To command this ship during the trial period, an exceptional officer was needed, one who inter–alia had to be an excellent seaman and be au fait with the latest theory on the behaviour of a ship at sea. The Admiralty’s choice was Captain Richards.Frederick William Richards was born on 30 November1833 in Wexford (now in the Republic of Ireland).
Educated at the Naval School New Cross, he entered the Royal Navy in his fifteenth year and served for severalyears on the Australian station. He was promoted to lieutenant in 1855, and was sent to the Pacific Station to join Ganges under the immediate command of Commander Hugh Talbot–Bourgoyne, who was afterwards lost when incommand of Captain.Following commands on the West Coast of Africa, he was promoted to Captain in 1866. Four years later he wasappointed to take command of the Indian troopship Jumma. The sea trials of ‘Devastation’ “It was arranged that Mr William Froude to whom the original researches on the behaviour of ships at sea had given great authority – should (direct the trials) and make scientific observations with the aid of novel instruments invented by himself.
His report was published as a Parliamentary paper and set the public mind at rest.” I have been unable to ascertain if Froude, as the foremost contributor to the body of knowledge on ship stability, had been approached by the Admiralty, or had himself pressed for his services to be employed. It is, however, very likelythe former, as in 1870 he had, in recognition of his work, been elected a member of the Royal Society (and received the Society’s Royal Medal in 1876). Thus in October 1873 Richards was appointed to command the Devastation, with a brief from the Admiralty to conduct exhaustive sea trials in order to settle the sea–going stability question once and for all.
The Devastation, and the other ships involved in the trials, were ordered to the Mediterranean. “Captain Richards’ appointment to this exceptional command was, therefore, in mark of the high estimation in which his professional qualifications were held by their Lordships, and this estimate was fully justified by the manner in which the trials were conducted and reported upon by Captain Richards.” The co–operation between the two men must have been excellent, because a warm friendship began, which continued until Froude’s death. Froude and Richards in South Africa After the Devastation trials, Richards was based at Chatham Dockyard in Kent until October 1878, when he was promoted to Commodore and appointed Senior Officer on the West Coast of Africa, with his flag in Boadicea. War with the Zulus was imminent, and he sailed for the Cape.
On his arrival, he received news of the British defeat at Isandhlwana (22nd February 1879), and promptly took his ship to Durban. There he, together with 227 other officers and men, formed a Naval Brigade, “which largely averted the danger of invasion after the Zulu victory at Isandhlwana.” Richards and his Brigade were present at the relief of Eshowe (3 April) and the Battle of Ulundi, which finally broke Cetshwayo’s army (3 July). In the midst of these Zululand activities, Froude arrived in Simon’s Town “as the guest of Commodore Richards”. (Lords, 1910). Whether he took ill while at the Cape, or he was sick before arrival, or what other circumstances arose, I have not been able to ascertain, but he died on 4 May 1879. It is certain that the two men did not see each other in South Africa. Froude lies in the Old Burying Ground, Simon’s Town.
Richard’s further career Richards and his men presumably returned to Boadicea after the Anglo–Zulu War, but reformed as the Naval Brigade with the start of the first Anglo–Boer War, and were present at the British defeat of Laing’s Nek (28 February 1881). Richards had been made a CB on 27 November 1879, and on 24 May 1881 was made KCB. On 9 June 1882 he was promoted to the rank of Rear–Admiral and terminated his service on the Cape Station and indeed his direct connection with South Africa. From 1882 to 1885 he served as Junior Lord of the Admiralty and then became Commander–in–Chief in the East Indies and thereafter of the China Station. In 1893 he was made Senior Lord of the Admiralty, the “highest position which a British Naval officer can occupy”. In 1898 he was promoted to the rank of Admiral of the Fleet. He retired in 1899 and died in Gloucestershire on 28 September 1912. While there is no evidence that he actually visited Richards Bay, he is commemorated in the name of the bay and, since the 1970s, port and town that has been created, not far from where he campaigned with his Naval Brigade.